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Theater Build: Mike's Money Pit - Page 2

post #31 of 253
Thread Starter 
Thanks! Yeah, it was a bit of a big decision, but ironically the pit was easy compared to the HVAC. I'm putting the finishing touches on a posting about that now. Hopefully I can post it in the next day or two, but I'm at CEDIA so it depends on free time.
post #32 of 253
Nice setup! Where in Silicon valley are you located?
post #33 of 253
This is already a superb build thread!

JustMike,

It's clear you have put a lot of thought into your screen size, which should help reduce possibility of "screen size remorse" in the future. And given the expense of many of our theaters, it's a major decision.

I agree that screen size choice is best done on personal criteria. Although I think "considered" personal criteria is best. Someone going only on instinct at first may not make the best decision in the long run. But careful thought, and testing, as you have done is clearly a wise move.

Thank goodness I persisted in testing out various screen sizes over time (projecting on my wall), before committing to my build. I originally thought I was going to use only a 94" diagonal 16:9 screen. Coming from a 42" plasma, 94" felt plenty cinematic.

But I found my taste in screen size varied over time, and varied depending on material and source quality. I never could settle on a strict size that seemed to capture everything I wanted, so I ended up putting the biggest screen I could on my wall and I use 4 way masking to vary the image size.

So I went from an original intent of 94" diagonal to the ability to have over 10 feet of width for CinemaScope, and up to about 135" diagonal for 1:85:1 content. Though I often watch lots of material at smaller sizes. (It's nice to be able to vary for guests and my wife. Some guests love a massive image. Others, including my wife, can find huge images overwhelming so I can make the image smaller in such cases).

Looks like you too are thinking "outta da box" in going for a Constant Image Area approach. I'm looking forward to seeing how you achieve this. (Will you be zooming on the projector front, to vary your image size?)

Quote:
Originally Posted by JustMike View Post


FYI, my masking system is going to be partially custom, since nobody makes a fully variable 4-way masking roll-down screen. Stay tuned for that article!

Interesting. I'm curious why you are going for a roll down screen. Are you putting a flat screen in the room, and dropping a projection screen for movie watching? (I missed it if you indicated this).

I managed 4-way masking, remote controlled, for under $5,000 and you can look at my build thread to see how. But seeing as you are using a roll down screen, my example will probably be of little use to you.

Anyway, keep up the great work on this thread! Thanks.
post #34 of 253
Thread Starter 
Quote:
Originally Posted by R Harkness View Post
This is already a superb build thread!
Hi Rich! Thanks! I especially appreciate that coming from you, since I really enjoyed your thread. I appreciated your being a bit of a lone CIA wolf in the CIH forum.

To answer your question, I'm using a roll-down because the screen wall was literally the only place in my house that I could put a big wall of bookshelves, which I desperately need. So, when the screen is not down, this room will be a library and music room. The center speaker will be built into the bookshelves, so there will basically be one section among the shelves that just has a fabric face on it, covering the center. KYDG has designed both diffusion and bass trapping into the bookshelves (along with the center, two Seaton SubMersive HPs, and the HVAC return ductwork!). If you squint at some of the pix at the top of this thread, you can sort of make that out.

Quote:
Looks like you too are thinking "outta da box" in going for a Constant Image Area approach. I'm looking forward to seeing how you achieve this. (Will you be zooming on the projector front, to vary your image size?)
The exact approach to vary the image size has yet to be determined, because it depends in part on the projector. I'm near certain that there will be a scaler involved, because I intend to play 2.35 material "pinned" to the bottom of the screen, since I find a lower height to be more comfortable to me. I can accomplish this with a scaler. To do other ratios, I will use the scaler, and combine with zooming of the projector if I'm able to do so.

I have a few requirements for the masking and ratio adaptation:
  1. For movies, it must be 100% automatic, triggered by the Kaleidescape system's aspect ratio triggers.
  2. It must either be fully variable, or it must support at a minimum the following ratios: 1.33:1, 1.375:1, 1.66:1, 1.78:1, 1.85:1, 2.20:1, 2.35:1, 2.40:1.
  3. It must support using different image sizes for different types of content. For example, 1.78:1 television will be smaller than 1.78 IMAX on Blu-ray. This is a "PMI 2.0"-inspired approach, although true PMI 2.0 uses projector zooming and brightness adjustment that I doubt that I will be able to match within my budget.
  4. It must be quiet.

Because I'm pretty demanding on all of these, I've built myself a set of requirements that are difficult to achieve. I believe I know how to do it, though. I won't go too much into it now, since I plan a whole posting on the topic, but the short answer is that I expect to use a motorized screen with an integrated top masking curtain, supplemented with roll down side masks that are able to move side to side. These side masks will be home brew.

I did read your thread in detail, and really hoped to use the panel system that you're using. Unfortunately, due to the design of the room, there was no place that I could stow the panels when not using the screen. I don't have enough space in the side walls to build pockets in for the panels, nor was it possible to tuck them back into the shelves.

It would have been great to use the panel system, because they could also have hidden the bookshelves during movie watching (in case of shiny or brightly colored books). As it is, we plan to build roller shades into the cabinetwork to hide the shelf area to either side of the screen.

Depending on how quickly I pass out on the airplane back from CEDIA tonight, I may manage to finish one or two of the postings I've been working on for this thread. Hope so!
post #35 of 253
Thread Starter 
Quote:
Originally Posted by fight4yu View Post
Nice setup! Where in Silicon valley are you located?
Thanks! I'm on the Peninsula.
post #36 of 253
Wow JustMike, you have quite a list of criteria to achieve. (And just seeing the word Kaleidescape in that list tells me it's a serious system!). Too bad about the Goelst panel system. I continue to be amazed at how flexible, precise, reliable and quiet this system has been. Now I'm really fascinated to see how your masking works out!

I had a hard list of criteria I wanted to achieve and almost drove myself insane, trying not to compromise. By the end of the build it even began to feel "not worth it" from fatigue. But now I'm reaping all the benefits of every detail I didn't give up on and I'm glad I was so pig-headed.

It looks like you are going into this with more general technical/construction knowledge than I had, so it looks promising for your project.

Later,
post #37 of 253
Thread Starter 
Quote:
Originally Posted by R Harkness View Post

By the end of the build it even began to feel "not worth it" from fatigue.,

Yes, I'm very, very deep into the "not worth it" phase with the overall remodel. Nothing like getting home from a long trip to a kitchen that's unusable and an entire house coated in dust.
post #38 of 253
Quote:
Originally Posted by JustMike View Post

Hi Rich! Thanks! I especially appreciate that coming from you, since I really enjoyed your thread. I appreciated your being a bit of a lone CIA wolf in the CIH forum.

To answer your question, I'm using a roll-down because the screen wall was literally the only place in my house that I could put a big wall of bookshelves, which I desperately need. So, when the screen is not down, this room will be a library and music room. The center speaker will be built into the bookshelves, so there will basically be one section among the shelves that just has a fabric face on it, covering the center. KYDG has designed both diffusion and bass trapping into the bookshelves (along with the center, two Seaton SubMersive HPs, and the HVAC return ductwork!). If you squint at some of the pix at the top of this thread, you can sort of make that out.


The exact approach to vary the image size has yet to be determined, because it depends in part on the projector. I'm near certain that there will be a scaler involved, because I intend to play 2.35 material "pinned" to the bottom of the screen, since I find a lower height to be more comfortable to me. I can accomplish this with a scaler. To do other ratios, I will use the scaler, and combine with zooming of the projector if I'm able to do so.

I have a few requirements for the masking and ratio adaptation:
  1. For movies, it must be 100% automatic, triggered by the Kaleidescape system's aspect ratio triggers.
  2. It must either be fully variable, or it must support at a minimum the following ratios: 1.33:1, 1.375:1, 1.66:1, 1.78:1, 1.85:1, 2.20:1, 2.35:1, 2.40:1.
  3. It must support using different image sizes for different types of content. For example, 1.78:1 television will be smaller than 1.78 IMAX on Blu-ray. This is a "PMI 2.0"-inspired approach, although true PMI 2.0 uses projector zooming and brightness adjustment that I doubt that I will be able to match within my budget.
  4. It must be quiet.

Because I'm pretty demanding on all of these, I've built myself a set of requirements that are difficult to achieve. I believe I know how to do it, though. I won't go too much into it now, since I plan a whole posting on the topic, but the short answer is that I expect to use a motorized screen with an integrated top masking curtain, supplemented with roll down side masks that are able to move side to side. These side masks will be home brew.

I did read your thread in detail, and really hoped to use the panel system that you're using. Unfortunately, due to the design of the room, there was no place that I could stow the panels when not using the screen. I don't have enough space in the side walls to build pockets in for the panels, nor was it possible to tuck them back into the shelves.

It would have been great to use the panel system, because they could also have hidden the bookshelves during movie watching (in case of shiny or brightly colored books). As it is, we plan to build roller shades into the cabinetwork to hide the shelf area to either side of the screen.

Depending on how quickly I pass out on the airplane back from CEDIA tonight, I may manage to finish one or two of the postings I've been working on for this thread. Hope so!

I am totally waiting for your info and how you build the 4-way masking system . I myself is using a roll-down screen (Seymour AV) as I am using it in my living room and I had a plasma behind it. Actually, I might even just need a horizontal mask at this point, as most content I watch is either 16:9 or 2.35.
post #39 of 253
Thread Starter 
There are a few lucky folks who can build a no holds barred home theater, with every aspect from the room's structure to its electrical supply and HVAC design optimized. Even fewer really, really lucky folks are able to have separate, dedicated music rooms and theater rooms, each optimized for the particular needs of that medium.

For most of us, the process of designing and building a theater room involves compromise. The art comes in making tradeoffs that preserve the intent of the room and maximize performance while working within the constraints of space, time and budget.

I touched on this subject a bit in my discussion of viewing angles up above in the post titled "The Tyranny of Trigonometry". In this post, I'll write a bit about some of the other compromises we've made in the design of my movie and music room -- what I've given up and what I've gained for it.

I'm sorry that I don't have a lot of new illustrations for this post, although I will re-use some of my earlier photos and renderings. I'm describing some design elements that haven't been built yet. More photos will follow at a later date.

Projection booth
One of the curses of modern electronics is the fact that nothing is 100% efficient, and most things are not even remotely close. So, for every bit of power that provides us entertainment, some extra amount of power gets turned into heat, and that heat has to be disposed of somehow.

At the source, this often means fan-forced cooling. Projectors use fans to cool their light sources and electronics. My Kaleidescape server has 12 hard drives in it, so its fans are working to keep those drives cool, along with the motherboard and power supply. The TiVo's fan is keeping its drive and electronics cool. There's an external drive on the TiVo, fans and drives in my NAS, fans and a drive in the Mac Mini... The list goes on and on.

In addition to the obvious heat being shed into the room, all of these fans and hard drives make a heck of a lot of noise that I sure don't want to have to listen to while trying to enjoy a movie.

In a perfect world, the projector would shine onto the screen through an optical port from an heavily-soundproofed projection booth. All of the equipment would reside there too, and the booth would have its own HVAC. This approach would have numerous advantages. All of the sound and all of the heat would be contained. The equipment would be centralized, with short, accessible cable runs between source devices and the projector. Even the aesthetics of the theater would be improved by having the projector hidden away.

Unfortunately, my room's layout does not lend itself to having a projection booth. If I built a booth in the back of my currently-planned layout, it would block a window that I want to keep in place:



As you can see towards the right-hand side, in addition to blocking the picture window, a booth on this wall would also block easy access to the stairway door going upstairs. And, there would be no way to get HVAC ductwork to that space anyway. We could have flipped the room 180° and had the screen drop in front of the picture window, but then I would not have been able to put the center speaker behind the screen, which was a key desire of mine for realistic dialog rendering. I would not have been able to build the bookshelves I wanted. And, the front right speaker would have interfered with the stairway door, too.

So, at least for this theater, a booth is out. A slightly less perfect but still exceptionally good solution would be to have all of the equipment outside of the theater except the projector, while the projector would be mounted in a sealed box with a supply of cooling air and an optical port. We worked really, really hard to try to achieve this, and in the end we just couldn't do it. The issue was the air supply. With my 8' ceilings, we needed all available space to run HVAC for the theater occupants (see the next section). There was no way to get cooling air to the projector. It turns out that the enclosure would also be expensive. Very expensive. An engineered optical "port" for the projector to shine through runs several thousand dollars.

So, my approach is to isolate all of the equipment except for the projector outside the theater. It's in the adjoining kitchenette area, where it's easily accessible through a doorway if I need to get at it. But, with all of the media stored digitally, there's not much call to physically access the equipment, so that door will really stay closed during movies unless somebody needs to get a refill on the popcorn. The wall between kitchenette and theater is heavily insulated, and the door will be an absolute double-gasketed beast.

As for the projector, it stays in the room, so now a key criterion for its selection is that it be really, really quiet. This does constrain my projector choices somewhat, and it may rule out some models that I would otherwise lust after, like Sim2's gorgeous Lumis 3D Solo (budget is a roadblock on that one too!), but I think this is a good strategy in the long term. LED light sources are coming on strong, and if the liquid-cooled engine used in the Sim2 MICO series and the TruVue Vango is any indication, we should be able to expect some very quiet projectors in years to come. This year's Sony VPL-VW95ES is shaping up to be ultra quiet, even though it uses a lamp, and the VPL-VW1000ES is also supposed to be extremely quiet, even given its 2,000 lumen output.

I had hoped to make a projector selection at CEDIA, and I did get to see many of the contenders, although not the 95ES. There are at least a half-dozen projectors that should achieve excellent picture while maintaining a very quiet room, which is key to really enjoying the movie soundtrack. Now it will be a matter of trying to decide which I like best. Challenging since many are unreleased. More to come on this front!

Ductwork sizing
Funny enough, our biological metabolism generates a fair amount of heat in its own right, and our respiration produces humidity and CO2 that will, in a closed room, eventually build up to levels that are uncomfortable.

When KYDG does the complete design for a theater room, including HVAC, they actually employ computational fluid dynamics to ensure that the air flow from the HVAC system will carry away the stale air from audience members while delivering appropriately heated or cooled air to the room.

Keith Yates is also a passionate advocate for bringing large quantities of fresh air into the space -- dramatically more than ASHRAE standards would suggest.

My budget wouldn't allow the CFD simulation, but KYDG did consult with my mechanical contractor on the HVAC system, and we did the best we could to meet their exacting standards. This has been, without exaggeration, the most challenging facet of the entire project! You'd think that removing a supporting wall and creating a below-slab pit would be difficult, but they pale in comparison to trying to create an ultra-quiet HVAC system in a room with an 8' ceiling and no available space above that ceiling.

With HVAC, noise comes from two sources: the equipment itself, and "regenerated noise" from the movement of the air. Regenerated noise is largely a function of air velocity, and air velocity is dictated by air volume per unit time (cubic feet per minute, or CFM) and the cross sectional area of the ductwork.

The capsule summary of all of that is that if you want to move lots of air at a low velocity so that it's quiet, you need really big ducts. With an 8' ceiling, you just can't have them!

While we can't have really big ducts, we can have fairly big ducts. The supply ductwork in my room has an interior dimension of 6" x 24". KYDG's experts would have preferred 10" x 24" or more, but this was the best we could reasonably do. All supply and return ductwork is fabricated from fiberglass ductboard, which has some wonderful advantages. Key among them is that it tends to absorb noise, both stray mechanical noise from the theater, and also any regenerated noise that may creep in as the air has to navigate some of the transitions in the ductwork.

The supply ducts are built into the room's perimeter soffits. You can see these in some of the pictures earlier in the thread, like this one. The ductwork is the black rectangular structure in the upper left, with the metal foil coating on the underside.



The air supply comes from the mechanical area, over the top of the kitchenette and bathroom, and enters the theater in the front left corner. You can see the rectangular cutout high on the wall in this photo, which was taken before the soffit was built:



It splits at that point, and basically encircles the room, forming a complete ring. The diffusers (large honeycomb types) will be in the soffit in the back of the room. The return air registers will be built into the lower cabinets in the front of the room, with the ductwork running up the wall behind the bookcases where they join into a common trunk and exit parallel to the supply ductwork, running over the kitchenette and bath and out to the mechanical space.

So, this was the compromise: we had to trade duct size against headroom. There's an obvious practical limit -- the ducts can't be so large that you can't walk under them. Before you reach that point, though, you encounter the point where it's walkable, but ugly and uncomfortable. Through trial and error with some mockups, we eventually settled for having the bottom of the perimeter soffit at about 7'4" from the floor. The ceiling height in the kitchenette and bath are similar.

This is pretty low, but since the main portion of the theater room is a full 8' from the slab level (9' above the pit), it doesn't feel oppressive. Even in the confines of the kitchenette, it's not bad. And, it allowed us to keep the duct sizing to a point where we can target having the room be an NC-15 in terms of noise. Many of KYDG's projects achieve much lower ratings than this (NC-5 in some cases), but this was a practical limit in my space, and it should still be very good.

We also had to trade off on the fresh air supply. A heat recovery ventilator (HRV) would introduce unacceptable levels of noise into the duct system, and achieving KYDG's desired rates of fresh air exchange would have pushed the overall CFM up too high in the downsized ducts, causing unacceptable regenerated noise. So, we will instead use a passive "mixing box" to bring fresh air into the system. In California's temperate climate, this won't be too bad from an energy standpoint, and it will only run when the room is in use. With the passive system and reduced CFM, my room will meet, but not exceed, ASHRAE standards with a "full house" crowd. I don't expect to have full house crowds often, so in practice I should have a comfortable fresh air supply.

Soundproofing
One of the reasons that it made sense to "settle" for an NC-15 noise level in this room is that, with certain exceptions, it's really not heavily soundproofed. This is anathema to most theater designs, where keeping external noises out is as important as keeping the theater's audio from distrubing others in the home.

In the case of my theater, though, the room resides below the finished level of the house, and as we've already discussed, the ceiling is 8'. There was no practical way to isolate the theater from the level above without unacceptable loss of ceiling height in the theater, or major and impractical changes to the flooring system above.

Fortunately, since I'm single, if I'm in the theater, then the only inhabitants of the house that can make noise or be disturbed by the theater are my cats. I don't have any neighbors close enough to the house to be bothered by audio leakage from the theater. Therefore, for me, having minimal isolation between the theater and the upper floor was an accpetable compromise.

Where we did put some effort is into soundproofing of the exterior walls, and the wall and door between the theater and the kitchenette. The kitchenette wall is insulated and will be double-drywalled on the kitchenette side to add some additional mass. I already mentioned the massive door.

Happily, the front wall of the theater (white in the photo above) is actually below grade, so it is extremely well isolated from outside noises. On the other side, my house is on a fairly quiet street, but cars do drive past. The spray foam insulation in the two exterior walls is a good sound insulator, and then the interior is sheathed with plywood and 5/8" drywall, which provides a lot of mass to help deaden any transmitted sound. Here's the photo I posted before to show the foam. The first picture in this post shows the wall after the plywood was added.



We are also mounting all of the equipment racks and the beverage refrigerator on sound isolation pads in the kitchenette, and I'm doing the same with the refrigerator in the upstairs kitchen (which is above the front part of the theater). The rack closet will be lined with rigid fiberglass board to help deaden the mechanical noises, and the ceiling in the kitchenette area will have acoustical treatment to help deaden what would otherwise be a relatively reverberant space.

I may also have the control system cut the power to the upstairs fridge and/or kitchenette beverage fridge during theater use if we still get hum leaking into the space. The HVAC compressors have been mounted at the farthest possible point from the theater, and the air handler will be vibration isolated from both the slab and from the supply and return ductwork.

The overall result of all of this effort should be that the room will be very quiet -- quiet enough to enjoy nuances in movie soundtracks and audio recordings -- but it will not be able to keep out loud external noises.

The Front Wall (Bookcases and Speakers)
I alluded to this above in response to Rich Harkness's question, but let me give a bit more detail.

I have a fairly substantial library of books, and nowhere to put them. When remodeling the house, I considered many options for possible bookcase locations, and the best possible place was the front wall of the theater, behind the screen. As you might imagine, this did complicate the design! But, it also has some nice benefits, as it turns out.

Acoustically, of course, Keith would prefer for the theater to have a engineered front baffle wall with integral speakers behind an acoustically transparent screen and stretched fabric. He also usually uses Genelec speakers, because (as I understand it) they're predictable, consistent, and have extraordinary headroom.

I, on the other hand, already own a set of Aerial Model 9 floor standing speakers that I chose after over a year of detailed listening tests and a 30-day in-home audition. I am rather attached to them. The CC-5 is also the best center speaker I've ever heard, so I really wanted to use it as well.

If this were strictly a movie room, I might have gone the Genelec route (assuming I could have found budget for them), because they really are quite spectacular in that application. But, this is a combination music and movie room, and I actually expect music to outweigh movies in terms of sheer hours of use. So, I opted to keep the Model 9s whose sound I chose so carefully.

KYDG designed the bookcase system based on a sketch by my builder. Unlike a typical bookcase, the back of the upper cabinets will be cloth over acoustical treatments (a combination of diffusion and bass trapping). The books themselves will provide a degree of diffusion. Here's a reminder of roughly what the shelves will look like when the screen is down. I think it's clearest in one of the non-textured early renderings, even though this rendering doesn't show the rest of the room accurately since it doesn't include the pit at all:



The lower cabinets are also tightly integrated into the design. The left and right outer sections house the HVAC return intakes (through grilles in the doors). The center two sections house two of the Seaton SubMersive HP subwoofers. The remaining sections will be available for additional storage, and to hold game consoles or other equipment that might want to live in the room.

The entire cabinet system will be built out fairly substantially from the wall framing behind. This gives space behind the upper shelves for the acoustical materials, and also allows for the HVAC ductwork to reach the intakes in the lower cabinets. The CC-5 is an extraordinarily deep speaker, so this depth works to our advantage there as well. KYDG designed the specific mounting of the speaker within the cabinet to provide a solid mounting, good acoustical surroundings, and proper aim of the speaker for the listening positions.

To accommodate the Model 9s as floor standers, we designed the stage to provide some placement flexibility. Its height was designed to split the difference between the original floor level and the sunken front row. This both provides a step down to reach the front row, and also ensures that the speakers don't get too high above ear level for the front (main) row, particularly for music enjoyment. As a reminder, here's the final design, showing the stage:



Summary
If you've read this far, I'm impressed! These were the major compromises made along the way to getting this room built, at least thus far. I hope this was an interesting post. Please fire away with questions if I've been unclear!

[edited to correct a few typos]
post #40 of 253
Mike

It looks like its going to be a wonderful HT and I for one will be following your progress.

Thanks for posting all the pictures and the "brainwork" behind it - Im impressed

regards

dj
post #41 of 253
Thread Starter 
Thanks, d.j.! Happy you're enjoying it.

On the plane back from CEDIA, I also wrote most of the article on the KYDG bass optimization system. I need to put together a little bit more info for that one, and then it will be coming soon. I think people will be pretty interested in it!
post #42 of 253
Quote:
Originally Posted by JustMike View Post

I think people will be pretty interested in it!

You got that right! But really, the whole thread has been nice to follow. While you're flexibility and willingness to go to great lengths can't be matched by a lot of us, it's very interesting to read your thought process and compromises. Your thoroughness is appreciated.

Fred
post #43 of 253
Thread Starter 

Seven subwoofers?!  Surely you can't be serious!

 

I am serious, and don't call me Shirley.

Invariably, when I tell people that there will be seven subwoofers in my theater, their reaction is something like, "Holy crap! Won't your neighbors' neighbor complain?!"

They naturally assume that I'm putting in more subs because I want more bass. But that's not true. I'm putting in more subs because I want better bass!

This posting is about why there are seven subs, why there are two types, and how we're treating the bass frequency response of the room. It's a particularly exciting topic, because this is an area where Keith Yates is doing something pretty unusual. I'll do my best to explain the idea.

No, really. Seven?
Yeah, really. I can explain the first three subs pretty easily. By using a trio of Seaton SubMersive HP subs, we could accomplish one of two things. We could blow the windows into the street and scare off the local fauna. Or, we could turn all three subs down in volume, so that they share the load to produce powerful but not overwhelming bass with plenty of headroom left over. Then, we could use that extra headroom by EQing the subs to play lower in frequency.

You may have guessed that we'll be taking the second approach, and sparing both the windows and the fauna. We should have meaningful in-room response down to 10Hz or so, where a surprising amount of content resides in movie soundtracks.

That explains three. And the other four are...?
The other four subs are Velodyne SC-IW in-wall subs, which are compact but capable subwoofers designed to go into a standard 2x4 studded wall. What are they for, and why are there four?

As everybody knows, one of the big problems with bass frequencies in any sort of home environment is that the wavelengths of low frequency sound waves are roughly comparable to the size of the room itself. This causes problems with interference, as these long waves reflect from surfaces and interfere with each other, producing noticeable peaks and valleys in the frequency response of the room.

If the bass is radiating from a single source, or even two sources the same distance from a wall (like stereo speakers), these interference patterns can be dramatically destructive to the sound quality of the room -- leaving "humps" and "suck-outs" that can only be inadequately treated with EQ, since an EQ can adjust the response for one spot in the room, but really can't make the response more even. Delays and changes in speaker placement can also help, but only to a degree.

What to do?

First, the seating positions in my new room have been designed so that they don't fall in the direct center between any two walls. This avoids a particularly dangerous zone for standing wave interference.

Second, it's helpful to use acoustical treatments that will absorb bass energy reaching the walls and ceiling, so that the reflected waves are not as strong, and the interference is not as pronounced. This bass trapping has been done in my room using a combination of semi-rigid fiberglass in large areas like the ceiling and front wall, and proprietary KYDG materials in particularly sensitive zones in corners and along the back wall.

Third, and most interesting, we are using a diversity of sources. By spreading the sources of bass energy around the room, we change the interference patterns in a way that minimizes the seat-to-seat variations in response.

This is where the Velodynes come in. Because they're compact and can be concealed easily behind the stretched fabric walls and ceiling, they can be moved to where they'll do the most good at evening out the room response at the seating locations, which is what we are trying to achieve.

But, how do you determine where to put the subwoofers so that you achieve this evenness of response? Trial and error would be one approach, and people often employ this approach with one sub. It would be pretty tedious to try every possible location, though, and when you start with three subs and consider adding even more to arrive at a best-fit sort of solution, it would rapidly become almost inconceivable. It would require an almost fanatical, robotic dedication.

So, Keith and his team built a fanatical robot. Or, more accurately, they built bass modeling software.

Meet the BOSS
Starting with a 3D model of the room, a selection of allowable subwoofer positions, and a minimum and maximum number of subs, the software performs computational fluid dynamic and finite element analytic simulation of the room. Yes, really.

The system is called "BOSS", for Bass Optimization Specification Service. It's the approach acoustics professors have been promising would someday solve the basic physics problem of bad bass quality in residential-size rooms.

After creating a 3D CAD room model, Keith's team brings it into Finite Element software, where it's "meshed". Unlike most "modal prediction" programs, BOSS doesn't force the model to be perfectly rectangular in shape. The room can have alcoves, a cathedral ceiling, soffits, raised seating platforms, an L-shaped layout, even a geodesic dome -- in any combination! In my case, the software had to account for French doors, a big flexy window, a pony wall and the dug-out front-row "Money Pit".

Importantly, BOSS "sees" whatever elements made it into the meshed model, including the room's construction, how stiff the individual wall, ceiling, floor, window and door assemblies are, and so on -- these are all part of the mix that makes bass.

Starting with a subwoofer in some position that's physically and aesthetically acceptable, the system computes the bass response at every seating location -- essentially a simulated tone sweep. Then, it tries another position, and repeats the process. And again for the next position, and the next, and the next. Here are a couple of images showing some of the possible subwoofer locations that the software considered for my room. These renderings are from a slightly earlier pass, so not all the locations are shown, and a few things are different, but you get the idea.





All this data is piped to analysis and optimization software, which Keith's team custom-programmed to "do the math" on all possible combinations of subwoofers -- for example, 3 subwoofers total in positions F2, R4, and B1. The algorithms then rank the combinations based on the physical results (including seat to seat variation) as well as psychoacoustic (perceptual) rules.

Many hours later, a very tired computer workstation reports its results. In my case, it computed and ranked 19,448 subwoofer layout combinations! With two of the Seatons in the lower center section of the front wall cabinets (F1 & F2) and the third in the former fireplace on the left wall of the theater (L1), BOSS called for four of the Velodynes to achieve the required smoothing. Three are in the ceiling of the room starting in the center left (C5, C6) and working over to the right rear (C1). One will go on the right rear wall (near where the surround is shown in the second image), to be concealed behind the stretched fabric.

Here's a photo taken today. You can see the three Velodyne subs up in the ceiling (they're masked off because they were doing the black paint today). The wall-mount sub isn't in yet.



These Velodyne subs (along with the placement of the third Seaton in the left wall) provide the diversity of sources to even out the bass response at the seating locations.

SUPER COOL: KYDG has provided me with an animation to show the results of their analysis! It's below, but a little background first.

Back when I was shopping for speakers, I heard a demo of the Aerial SW-12 subwoofer, and was really impressed by it. So impressed that when I saw a pair of used SW12s advertised online a couple of years ago, I bought them for eventual use in the theater. Since I had those subs, they were the starting point of this simulation.

The left side of the video shows the effects of a simulated 15-80Hz tone sweep as produced by those two Aerial subs sitting on the stage. (Their woofer outlines are the dark red circles.) The audience head positions are the darker, more opaque discs.

This "pressure slice" as Keith calls it is taken at ear height, 41 inches above the floor. The color in the slice represents the level (SPL). Dark blue is the lowest, and dark red the highest. The 'rainbow' spectrum in between spans a 40dB range, meaning if you freeze a sweep at a particular bass frequency and look at the level at different locations, you'll find the response can vary by as much as 40 decibels!

The right side of the video shows the result of the same sweep as played by the 7-subwoofer combination that turned out to be the highest-ranking configuration for my particular room. Be sure to view in HD!!



If you look carefully at the video, you will see that the levels vary substantially across the frequency range in both versions. But, crucially, the seat-to-seat variation is reduced in the one on the right. The BOSS algorithm does consider the overall response flatness, but it doesn't give it much weight, since we can flatten the overall response with EQ. What it cares more about is that variation from seat to seat that the EQ can't do anything about.

You can see a really good example in the frame below, extracted from the video. There's a huge difference in the bass levels between the front and back row in that frame in the original sweep. Compare with the optimized response on the right. There are definitely some points in the optimized sweep where the response is uneven, but I think the improvement is also pretty clear.



How good is it?
This process has been used for several other recent KYDG projects that are now complete. Actual seat-by-seat measurements of the completed rooms track the predicted values to within 1-2dB, so the modeling is proving to be an accurate predictor of results in the field.

I had some very noticeable bass response problems in my old room before we started this whole project. As a bass player, I care a lot about the clarity, balance and performance of those lower octaves, so I am really looking forward to hearing the results from KYDG's design. As well, having experienced some movie soundtracks in rooms with extended bass response, I can hardly wait to cue up some great movie content and enjoy the visceral impact that only powerful, deep bass can give!

Sincere thanks to Keith and KYDG for providing the animations and renderings for this posting, and for spending hours on the phone explaining the concepts behind this approach. I hope I haven't butchered any of the material too badly. Any errors are of course mine. I will do my best to answer questions, but I may be unable to answer all questions due to limitations in my own knowledge!

Sorry this post was a long time in coming, but I hope everybody enjoyed it!


Edited by JustMike - 6/11/12 at 12:11am
post #44 of 253
Wow this looks like its going to turn out really well! subscribed!

I can't tell from the render but are you going to be using a 16x9 screen?

-Kevin
post #45 of 253
Thanks for sharing Mike. From your description, it seems like difference between unoptomized and optomized animations is only the number, type, and location of the subs, and that both animations account for the bass trapping and other treatments that you've planned to use - is that right?
post #46 of 253
Thread Starter 
Thanks, Kevin! Yes, it's a 16:9 screen, but I'm going to be using a type of "Constant Area approach with a custom masking system. That, in fact, is the subject of the next article I have planned! :-)

Fred, the answer to your question is "yes and no". You're correct that the two animations just represent the difference between the subwoofer configurations.

However, the animations I have here are of the "base model" of my room, which would only include bass treatments if the room already had existing treatments built in (mine did not).

So, what you see here is representative of the untreated room. The animations help KYDG identify locations where treatments would be especially helpful in mitigating low frequency problems.

Part of the value of doing the animations is that they show how the basic geometry -- the available subwoofer positions, the audience locations, and the room's size, shape and physical make-up -- conspire to distort low frequency response.

Once the base model is analyzed, optimized & animated, the "elective" stuff (including bass traps) can be added. The same FEA/CFD platform is used to model and optimize low frequency treatments.
post #47 of 253
Thread Starter 
Thanks David! I can hardly wait to hear it myself. I expect to be very happy with the results.

I find myself torn, too -- I know that we made a number of compromises on my project due to practicalities and budget, so I'll always wonder what a truly no holds barred system would sound like. But if I hear one, I may bankrupt myself.
post #48 of 253
These threads are a love and hate this for me. I love to follow along and learn as much as I can. But being at the start of my career having just finished school the wait until I can start my own build thread is going to kill me
post #49 of 253
Forgot to ask. Are you finished the custom masking system or is this something that you are going to develop yourself ?

I am actually very interested in developing my own masking system for my future projector setup (I might not know an LCOS from a DLA but I know my electronics). I've actually started to put some thought into how to do it so its both smooth and quiet.
post #50 of 253
Thread Starter 
If it makes you feel any better at all, I'm still using gear that I bought years ago. One thing that's nice about good HT gear, especially on the audio side, is that there's not much reason to replace it. I'm thinking here about things like power amplifiers, for example. Processors are more problematic, although my Lexicon lasted many years before Blu-ray finally forced an upgrade for me.

My contractor and I have designed the masking system, but it hasn't been built yet. The next article will talk about the plan, but I'm afraid there won't be many pretty pictures yet because so far the cavity in the ceiling where the screen goes is just an empty black hole!
post #51 of 253
I use to be into the whole audiophile game when i was young and broke. My audio gear is far from great but it will be fine while I build up the video side. I know alot of ppl will tell you to buy the A/V gear after you have built the room, but that just isn't an option for alot of us. So the plan is to collect gear over the next few years (while saving for a down payment on a house), and learn as much as I can about designing and construction dedicated HTs. I figure by the time I have the house and can afford the gear I want ill be a guru
post #52 of 253
Quote:
Originally Posted by JustMike View Post



Very Cool Thread, thanks for taking the time to explain your design in such great detail..

I've been waiting on the next update to see if you discuss them, but Ill go ahead and ask... regarding the thin panels on your ceiling, are they a binary diffuser design, a low pass filter, or something more sinister...

Brad
post #53 of 253
Thread Starter 
Hi Brad!

Yes, it has taken longer than I had hoped to get the next article ready, and in any event it will be about the screen masking system rather than the acoustical treatments.

Anyway, yes, those are so-called binary diffuser panels. In the photo, we were only part of the way through installing them. Ultimately, they will be up on about the back 1/3 of the ceiling, plus the sides of the ceiling area up to the front of the room (sort of a "U" with really skinny uprights). I'll post some pictures when they're all up.
post #54 of 253
Thread Starter 
A little more info on those panels. They provide diffusion in the 8-16kHz range, which gives some "air" to the top octave. Below that, the fiberglass behind them provides absorption down to about 250Hz.
post #55 of 253
Thanks for the follow up on the Binary panels Mike. One last question, did KYDG design and build the panels or were you able to purchase prefab panel/sheets from somewhere?

Thanks
Brad
post #56 of 253
Looks like a really nicely designed room. I really like all the thought and design that has gone into your room and set up of equipment, especially the subwoofers. I have thought about a design that uses sealed subs up front and four of these spread around the room. http://www.bgcorp.com/subwoofer-speakers.html
Reply
Reply
post #57 of 253
Thread Starter 
Quote:
Originally Posted by KNKKNK View Post

Thanks for the follow up on the Binary panels Mike. One last question, did KYDG design and build the panels or were you able to purchase prefab panel/sheets from somewhere?

Thanks
Brad

Hi Brad,

KYDG supplied the panels, but they are made by RPG. The room treatments are a mix of common materials, specialty products like these from acoustic materials vendors, and KYDG-custom products.
post #58 of 253
Thread Starter 
Mike, I'm not familiar with those, but they look similar in concept as in-wall subs. The great thing about those is that if you're doing stretched fabric, you can really put them anywhere!
post #59 of 253
Quote:
Originally Posted by HFGuy View Post

I figure by the time I have the house and can afford the gear I want ill be a guru

By the time I have the house and can afford the gear I want, I'll be a corpse.
post #60 of 253
Quote:
Originally Posted by LastButNotLeast View Post

By the time I have the house and can afford the gear I want, I'll be a corpse.


Unfortunately over the last year I think I have developed tinnitus or something (i still have to book an appointment to have a hearing test). My family doc doesnt think its the case but its very disheartening to not be able to enjoy audio. Basically I develop a headache if I listen to audio for any amount of time at any volume I guess Ill have to spend more money on the video side of HT.
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